Honestly John, you should just choose another game. Civ V without the expansions is extremely accessible and you should get good at that before moving on to harder games. The Endless games are not for people who are new to the genre.
Update on the campaign. The good news is that the tide has turned against the necrophages. my plan paid off after a load of save scumming. Striking them first when their army was split meant i prevailed. Helped that they retreated twice softening their units. It was then a case of divide and conquer and we destroyed their main army. It was a great cost to my one as well as the battle to break the back of their main army cost me 3/4 of my own one.
Now there is only one province to take and oh boy its going to be tricky. Its their last stand and they are just building forces up. I'm hoping perhaps to expand a bit more and bring the entire force down on them and see what happens. If they keep sending minor incursions, i might hold them off indefinitely, but they had it coming.